Oscillation generator



May 8, 1945- H. B. sHAPlRo 2,375,695

oscILLA'TIo'N GENRAToR l Filed sept. 26. 1942 2 Skeeter-sheety 1 My s,41945. H. B. SHAPIRO l 2,375,695

osvlcILLATIoN `GENERATOR Filed sept.2s, 1942 2 sneeisfsheet, 2

HG. AE

N V EN TOR.

HABE Y .SNAP/ea Now BY Juol CML CHANGE 0F NAME hunny B. SHAPE/z PatentedMay8, 1945 man "quency osoILLATIoN GENERATOR, "Harry B. Shapiro,levelandHeights, Ohio, now i by judicial cha-nge of name Harry Bryant Shaper,assigner to The Brush Development Company,A Cleve @Ohioi'` y l land,Ohio, a corporationo'f Application september ze, 194.2, serial No.459,756 11` claims. (015250-361 c c tooscillation generators and, 'moreparticularly, to oscillation generators of` `the variable frequencytype,

When taking curves exemplifying `the frequen'cyeresponse of varioustransducers Vsuch as c invention relates telephone receivers,loudspeakers `'and the like, it

is advantageous to utilize an oscillationgenerator that` provides anoutput current which` may be caused to vary over a wide range ofaudiofre- Y types such,`for example, as the audio beat frequenoy type whereinthe output, `at `audio Vfre-` lis obtained throughthe interaction ofthecurrents from two relatively high freoutput q'e'ifc'y oscillators, oneiixedfand one variable. 55

The generator, furthermoramay `be of the type that is mechanicallytunableover a specific range or thetuning thereof maybe"-e1ec`tronically controlled, the only `requirement `.being thatitshall clude a frequency-determining element -theeffective impedanceoflwhich may be caused to varyby the aforementioned reactance tube. i'

For example, when practicing the invention in connection with a beatfrequency oscillation genquencies and which., if ldesired, may be causedto erator, the reactance tube may be supplied with` wobble or Warble a"predeterminedpercentage ,c warble-control` potentials from a variablelow above and below any frequency within said range. c frequencyoscillator 'and a biasing potential for Previous to `this invention,``the warble has the tube,` derived from'the generator itself, may-bebeen obtained through utilization of `a mechanin utilized to `cause thegain vtherein to `v'alryjafs*a callyvdriven tuning device, suchasan'auxiliary l5 function of the frequency fof the youtput, frcm theshunt capacitor of the type shown in the patent to generator.Alternatively, the reactance jtube may Farrington No.` 2,205,190. t Withsuchfa device, the be provided with a xed'biasand be Supplied "with lwarble frequency is not a constant percentage control potentials fromthe warble oscillator, the of the Iparticular base frequency beingwarbled amplitude'of the saidpoten'tials being `causez'ito `but alwayshas a fixed band Widthunless auxiliary 2o vary as a function of 'thefrequency of the outcompensating means are employed. c i put from thegenerator'. VIn a still furtherem- Itis, accordingly, an object of thiskinvention to bodiment, a varying` biasing Vpotential y may 'be providean` oscillation generatonthe `output from derived `from the variablehigh frequency oscil- Which maybe warbled a, predetermined per; c latorcomprised in the generator'instead offrom centage of any frequencywithin its range. t the output of the generatoritself andsuch poten-Another object is to providea warble oscillatial maybe applied to thereactancejtube directly tor wherein the percentage of frequency swing'`is or it"may` be utilized to control "the amplitudejof adjustable at thewill of the operator. i the potentials supplied thereto from thell'owAnotheriobject is toprovide a warbleoscillaf t ,i frequency oscillator.c Y j tor wherein the percentage offrequency swing, 3U `The novelfeatures considered characteristic after having once been adjusted,remains substanof the `invention areset `forth withparticularityn tiallyconstant over the output range. the appended claims. `Theflnventionitself, `howl,Another object is to provide `a warble, oscilever, bothfasto its organization andfitsmethod lator the base frequencies 'of whichare substan 0f Operation, together with further "Ubll'sjn'd tiallyindependent of the Warble-control devices. advantages "thereof, 'Willbest be understood from A still further object is to provideanoscillator the following .description j0`f ,Certain "SD'GIG of the typedescribed thai-,shall not require meembodiments, when read in connectionwith the c hanically moving parts for obtaining the warble accompanying.drawingSQin Whihf c effect. i f c t `Figure lis" acircuitdiagramexemplifying `an In accordance with the invention, electronic 40embOdlment of heinvention; c ,c warble-controlmeans are substitutedfortheusual Figure 2 is a circuit diagram exempllfyin'g jan mechanicallyactuated warble` capacitor, such alternative'embodime'nt; Bildf 1 r imeans, preferably, `including a reaetanee tube Figure 3 isacircuitdia'gramlexemplifying anthat `may be `so energized and connectedas to cyother `embodiment of theinvention. c clically cause a minorchange inthe effective in- In all figures of the drawings,identicaleleinent's ductance, capacity or resistance of a frequencyc areSimilarly designated. i c determining network in an oscillationgenerator, Referring to Figure v,1 ofthe drawings, 1anlmautomaticallyunder control of a current or pobodiment of the invention mayincludeaivariable tenuar `denveafnm said generator. The osbeat-frequencygenerator, indicated eenerally'bv cillation generator may be of any ofthe usual the Ilumelial D10Vding`a`n Output Current at audio, supersonicor radio frequency,whichgen` 5 eratorincludesla frequencyi-deterniiningnetwork,V or a tank circuitsuch asc might beconstituted fby an'inductorSshuntedbya capacitor l. L'I'h'eteln frequency determining networkAisntenrlleu"to f include a, xed or variable tuned circuit, a variableor fixed capacitor, inductor or resistor, or any other circuit elementor network that plays a part in determining th'e frequency of theoscillations generated and/or delivered to an output circuit.

For the purpose of varying the effective reactl ance of the inductor 3,it may be connected across the output circuit of a thermionic tube 1 ofthe variable mu pentode type, such as the 956, and connections areprovided whereby the tube draws a current that lags the alternatingpotential appearing across the inductor. l

To obtain proper grid excitation for the tube, at the frequency of thepotential appearing across the inductor 3, the connections include aphase shifting network, constituted by a resistor 9 in l l R c thecurrent in the said capacitor will be substantially in phase with thepotential across the tank circuit, with the result that the alternatingpotential appearing across the capacitor I l, which is applied to thecontrol grid I3 of the reactancev tube, lags the potential impressedacross the network from the inductor and the tube I I, therefore, drawsa lagging current and functions as an inductor .connected in shunt tothe inductor 3.

Preferably, the high potential supply circuit for the reactance tubeincludes an inductor I9 that offers highreactance at the frequency de'-termined by the inductor 3 and the capacitor 5.

For the purpose of introducing warble into the system, the extent ofwhich, or swing, increases `with increasing frequency ofthe outputcurrent from the generator, the control grid I3 of the reactance tube 1is connected to the cathode thereof by Way of a grid leak 2l, a resistor23 constituting the output circuit of a rectifier and a tapped resistor21 included in the output circuit of a low-frequency warble controloscillator 29.

'The rectifier 25 is supplied with input currents from the outputcircuit of the generator, the supply circuit including a low-pass filtersuch as a series resistor 3I and a shunt connected capacitor 33. Thepositive terminal of the rectifier output resistor 23 is conductivelyconnected to the cathode of the reactance tube and the negative terminalthereof to the grid of the tube, whereby the biasing potential suppliedto the grid I3 becomes less negative as the frequency of the outputcurrent fromltheg'enerator increases. The gain in the reactance tube,accordingly, increases With rising output frequency and thereactance-change, at'the warble oscillator rate, that it can cause, isthus automatically made greater at the high frequency end of the rangethan at the low frequency end.

Through proper choice of the values of the various circuit elementsillustrated, such as the resistors 23 and 21, the percentage offrequencyshift, or warble, may be controlled, and after once having beenset it remains constant over the entire output range.

applied to the warble' control tube 4I by the recti-A Should theconnection of the reactance tube to the inductor 3 disturb thecalibration of the oscillation generator, one or more padding capacitors3,5 may be employed for Icompensation.

'A modification of the invention is illustrated by Figure 2. In thatembodiment, the reactance tube 1 is connected to the frequencydetermining element 3 comprised in a variable oscillation generator insubstantially the same manner as described with reference to Figure 1. Arectifier 25 is also provided which gives an output current thatdecreases in response to increase in frequency of the output currentfrom the generator. The reactance tube 1, however, is given a fixed biasfrom a resistor 31 in the cathode circuit thereof and the control gridI3 therein is connected to the cathode by way of the resistor 2| andapotentiometer 39 included in the output circuit of a warble control tube4I, which may be of the variable muA type such as a 6SK7. Grid bias forthe Warble control tubedl is supplied by a circuit which includes theoutput resistor 23 of the rectifier 25 and a variable portion of thewarble oscillator output resistor 21. Accordingly, the amplitude of thesignal introduced from the warble control tube into the grid circuit ofthe reactance tube 1 is a function of the setting of the potentiometer39,of the bias, varying with frequency, supplied from the resistor 23and of the amount of the warble-oscillator output resistor 21 that isincluded in the circuit. The bias fier 25 may be permanently adjusted toselect the most favorable part of the mutual conductancegrid bias curve,if desired. f i

Instead of utilizing the output current from the beat frequencygenerator to provide a Warbleamplitude, or swing-control, essentiallythe same result-,may be obtained by making useof a portion of the outputcurrent from the variable high frequency oscillator. That is to say,referring to Figure 3, a portion of the output from the tunable highfrequency oscillator portion 45 of the generator may be fed to anauxiliaryamplilier 41 the output from which is supplied to therectifier' 25 that provides a unidirectional current which varies inaccordance with the frequency of the said oscillator. The rectifieroutputrnay be utilized for varying the effectiveness of a reactance tubeassociated with a frequency determining element or network in the fixedoscillator 49, as described in connection with Figure 1 or y Figure 2.

Inasmuch as many alternative modes 'of warble` control, by utilizing thevarying current provided by the rectifier, will be obvious to thoseskilled in the art without departing from `the spirit of the invention,they havev been merely indicated in Figure 3 by a rectangle 5I, with thegeneral designation warble-control devices. 7

' An'oscillation generator constructed in accordance with the inventionhas numerous advantages among which may be mentioned the following asperhaps being the most important:

' (al The integral of energy, in each band examined by means of thewarble, is constant.,`

(b) The band width at each point in the range, when warble isintroduced, is automatically so adjusted that no over-shooting of zerofrequency takes place at the low frequency end of the range. (c) Therate of warble is easily changed, which enables the avoidance of warblefrequencies that might coincide with resonance frequenciesof the metersor other indicating apparatus utilized.

(d) The percentage of warble is easily'changed,

` characterized in this: that the Other advantages, as well as`alternative embodiments of the invention, will be apparent to thoseskilled in the art. The invention, therefore, is not to be restricted bythe specific embodiments chosen for illustrative purposes, nor

rents to vary cyclically, and means responsive to the frequency of thegenerated currents for causing the percentage of cyclic variation to beconstant over the frequency-range of the oscillator.

2. An loscillation generator having an output circuit `and having agiven frequency` range, adjustable reactor means connected to saidoscilla- `tion generator for influencing the output frequency of saidoscillation generator within said frequency range, means interconnectingsaid output circuit with said reactor means and including means forestablishing a rst potential in accordance with currents delivered tothe output circuit of said oscillation generator, oscillator means forestablishing a second potential which varies cyclically, said first andsaid second potentials being added to establish asummation potential foradjusting the reactance of said reactor means for influencing the outputfrequency of said oscillation generator within its frequency range inaccordance with a constant percentage function of thefrequency of thecurrents delivered to the` said output circuit and in accordance withthev cyclically varying output from said oscillator.

3. The invention as set forth in claim 2 further frequency of saidoscillation generator is mechanically changeable Within its saidfrequencyrange, whereby said summation potential is altered to influencethe frequency of the output signal from said oscillation generator.

4. The invention as set forth in claim 2 further characterized in this:that the said means for establishing a first potential is a means forestablishing adirect current in accordance with the currents deliveredto the said output circuit of said oscillation generator.

5. The invention as set forth in claim A2 further characterized in this:.that the said adjustable reactor means includes a reactor tube having agrid and a cathode and whose grid voltage determines its reactance, saidsummation potential being applied to said reactance tube between thesaid grid and cathode.

6. The invention as set forth in claim 2 further characterized in this:that the said adjustable reactor means is a reactance tube having agridand a cathode and whose grid voltage determines its reactance, and thatsaid means for establishing the said first potential is means forestablishing av direct current potential.

7. The invention as set forth in claim 2 further 10; characterized inthis: that the said oscillationl generator is a beat frequencygenerator.

8. In combination, an oscillation generator having'a given frequencyrange, reactor means connected to said` oscillation generator foriniiuencing the frequency of the generated oscillations, means connectedto the said oscillation generator for causing the frequency of thegenerated currents to vary `cyclically, and means responsive to thefrequency of the generated currents for causing the percentage offrequency variation to be constant over the frequency-range of the saidoscillator.

9.` The invention as set forth in claim 8 further characterized in this:that the said reactor means includes a reactor tube whose grid voltagedetermines its reactance, and that the means responsive to the frequencyof the generated currents for causing the percentage of variation to beconstant over the frequency-range of the said oscillator is a means forvarying said grid voltage.

10. The invention as set forth in claim 8 further characterized in this:that said oscillation generator is a beat-frequency generator and its`frequency is mechanically changeable over substantially its entirefrequency range, and that` the said reactor means includes a reactortube whose grid voltage determines its reactance, and

. that the means responsive to the frequency of l the generated currentsfor causing the percentage of `variation to be constant over thefrequencyrange of the said oscillator is a means forvarying said gridvoltage.

11. An oscillation generator including a, frequency-determining reactorand having a generator output circuit; a thermionic tube having an inputcircuit, and having an output circuit connected effectively in parallelto said reactor; means for impressing on said input circuit a laggingpotential derived from said reactor;

.means for impressing oscillations at low frequency upon said inputcircuit; and means responsive to the frequency of the currents deliveredto said generator output circuit for determining the amplitude of saidimpressed low frequency oscillations.

i HARRY B. sHAPIRo, Now` by Judicial` Change of Name Harry B. Shaper.

